A tire usually comprises beads extended by sidewalls, the latter being joined by a crown ring itself surmounted radially on the outside by a tread.
This type of tire comprises a carcass reinforcement extending in the side walls and anchored in the beads, the said carcass reinforcement being formed by at least one stack of reinforcing elements substantially parallel to each other and coated with at least one rubber composition. Stack means either a ply formed in advance by calender-coating reinforcing elements between two layers of a rubber mix or a composite formed from a plurality of reinforcing elements coated in a rubber mix. The reinforcing elements can consist of wires or textile or metallic cords.
Tire beads, intended to be in abutment on the tire mounting rim, comprise a reinforcement ring for the bead disposed concentrically with the axis of rotation of the tire. This reinforcement ring serves for anchoring the carcass reinforcement. It is in general formed from a bead wire coated with a rubber mix to form a composite structure with a round cross section. A bead wire is a body formed from one or more reinforcing elements disposed so as to confer on the said structure a circumferential extension rigidity sufficient to take up the forces created in the carcass reinforcement by the inflation of the tire. The said bead wire may or may not have a round transverse section.
Whether the bead wire has a round section or not, it is usual to coat this bead wire with at least one rubber mix so as to obtain a toric ring with a round section.
In the most common tires, the carcass reinforcement is anchored on each reinforcement ring of the bead by partial coupling around the said ring in order to form an upturn extended radially upwards and coupled with the carcass reinforcement by at least one rubber mix.
The structure thus formed (carcass reinforcement, upturn and coupling mix) has high stiffness in flexure. However, this structure has sensitivity to breaking at the end of the upturn because of the position of the said end in a region of more or less strong flexure.
To reduce this sensitivity, it has been sought to put the end of the carcass reinforcement outside the flexure zone, by putting it in the tire sidewall or even under the crown.
This is also the reason why it has been proposed to develop tire bead structures not having an upturn end of the carcass reinforcement in the flexure zones (or more generally in the movement zones) of the tire.
In this type of solution, the upturn of the carcass reinforcement partially or completely surrounds the bead reinforcement ring.
The document EP 1 066 992 describes an architecture in which the end of the upturn of the carcass reinforcement partially surrounds the reinforcement ring of the bead so that its end is situated radially outside the said reinforcement ring.
Another type of construction of these tires is characterized by the fact that the carcass reinforcement is wound around the reinforcement ring of the bead so that the end of the said reinforcement is engaged between the reinforcement ring of the bead and the carcass reinforcement itself in order to make at least one complete turn of the said reinforcement ring of the bead. This particular arrangement also has the advantage of optimising the mechanical anchoring of the carcass reinforcement on the reinforcement ring of the bead.
However, producing these structures is tricky because of the difficulty of making the reinforcing elements of the carcass reinforcement take pronounced curvatures because of their return elasticity, normally described by the term “snappiness”.
An object of the invention concerns a device for producing this type of tire industrially, the elements of the method related to the use of this device.
The prior art concerning a method able to produce a tire close to the type described above is disclosed by way of example in the publication EP 1 024 033. This document reports on the possibility of engaging the end of the cylindrical sleeve between the reinforcement ring of the rim and the carcass reinforcement. This means remains limited by the fact that, during the implementation of this method, it is not possible to make the said carcass reinforcement make a complete turn around the reinforcement ring of the bead; the number of turns being counted on the inside diameter of the said reinforcement ring of the bead as the number of passages of the said carcass reinforcement stack minus one unit.
Moreover, so as to combat the “snappiness” of the reinforcing elements when these consist of metallic cables, EP 1 024 033 proposes to break the said reinforcement by applying a heavy rolling on the areas of the reinforcement intended to be subjected to the greatest curvature. It is nevertheless sought to avoid such an operation because of the localised plastic deformations that it causes the metallic reinforcing elements to undergo, which may be prejudicial to their endurance.